This conceptual paper deals with some of the implications that the use of social network sites, though not originally developed and conceived for learning purposes, have for schools and academic activities when they are used as tools able to modify and innovate teaching/learning practices and academic culture. Beside the differences that characterize the two contexts, the attention that social network tools are progressively gaining in schools and higher education practices and pedagogies requires adjustments in learning and teaching that should be constantly considered by educators and policy makers. These environments are also presenting new and crucial opportunities for teacher training and teachers' professional development. The purpose of the study is to reflect on some significant challenges and opportunities offered by social network sites, and how to exploit the latter, in relation to a number of themes. These themes have been identified as those that deserve better comprehension and further research investigation: communication between students and teachers and appropriate professional behaviours; pedagogical and technological challenges related to incorporating social networking practices into teaching and academic practices; how social networking can be exploited for teachers' professional training and development. The study also provides some implications for policy and practice.